Jacobs Drill Chuck Runout--

[mksj]

Today I just turned one of the components of my mill/drill chuck stack 180 degrees, and the runout went from 12 thou to one thou!

Sweet! The newer Jacobs drill chucks from China are quite poor by reports from others. At the price you pay for them, they should have better QC (and quality), but one needs to include the arbor in the equation. I use a Z-Live integrated arbor keyless 3MT chuck on my lathe tailstock, and it works like a dream. So it seems hit or miss. On the mill I like a keyed drill chuck so tooling does not fall out of the chuck when reversed, like threading. I need to get a bigger drill chuck, probably a ball bearing 5/8" Llambrich chuck.

 

[Bob V]

Hi John K, and thanks for the input,
I've finally taken pictures of my setup-- yes there is an adapter in the setup as can be seen in the photos and as I indicated in my first post about this.
-- I did get the runout down to less than one thou at the gage pin in the chuck in the pic when mounted in my old mill.
I plan to use dome dykem blue to try to see if there are any burrs or whatever up in the spindle-- but I think the inside of the spindle is OK.
The collets (nearly a full set came with the mill) are in pretty rough shape: quite a few are galled inside and I'm trying to see if I can rehab any of these-- would appreciate any tips on this--
It seems my major hurtle is the lack of availability of 5c collets at a reasonable price--

Thanks again for all the help--
Bob

 

[EmilioG]

The drill chuck jaws may be the culprit in some cases. I've read in Lautards MBSR #1, that using a ceramic rod, 1/4" dia. to lightly
grind the jaws, can help in reducing TIR. By lightly closing the jaws around the abrasive rod while it's spinning in the lathe, this is supposed to
grind the jaws ID evenly. Not sure if I would do this to a new set of jaws. I have back up sets of the older USA Jacobs 14n rebuild kits.
May be worth a try on slightly worn jaws? Another source of wear on a Jacobs, is the sleeve. The ID bearing surfaces wear over time. I've also read that using a .0001" indicator is better for checking TIR, along with a dowel pin size that is half the chucks capacity. (Jacobs 14n- 1/4" dowel pin). Precision dowel pins are supposedly the straightest pins one can easily find and use.

 

[Wreck™Wreck]

It is a DRILL CHUCK, these are commonly used for DRILLING rough holes at rapid metal removal rates. If you require a very high level of diametral accuracy do not use one for such purposes.